A full duplex radio (FDR) or full duplex communication scheme refers to a communication scheme for simultaneously supporting transmission and reception using the same resource in one user equipment (UE). In this case, the same resource refers to the same time and the same frequency. FDR communication or full duplex communication is referred to as two-way communication.
FIG. 1 is a conceptual diagram illustrating a UE and a base station (BS), which support FDR.
Referring to FIG. 1, in a network state that supports FDR, there are three types of interferences. First interference is intra-device self-interference. The intra-device self-interference means that signals transmitted from a transmission (Tx) antenna and received by a receiving (Rx) antenna act as interference in one BS or UE. Since the signals transmitted from the Tx antenna are transmitted with high power and a distance between the Tx antenna and the Rx antenna is short, the transmitted signals are received by the Rx antenna without almost of attenuation, and thus, are received with higher power than a desired signal. Second interference is UE to UE inter-link interference. In a network that supports FDR, the UE to UE inter-link interference is increasingly caused. The UE to UE inter-link interference refers to interference caused by uplink signals that are transmitted from a UE and received by a neighboring UE. Third interference is BS to BS inter-link interference. Similarly, in a network state that supports FDR, BS to BS inter-link interference is increasingly caused. The BS to BS inter-link interference refers to interference caused by signals that are transmitted between BSs or heterogeneous BSs (pico, femto, and relay) in a HetNet state and received by an Rx antenna of another BS.
Among the three types of interferences, the intra-device self-interference (hereinafter, referred to as self-interference) is influence of interference caused only in FDR. In order to manage FDR, the most serious problem is cancellation of self-interference.